Electro- and Photochemical
Water Oxidation on Ligand-free
Co<sub>3</sub>O<sub>4</sub> Nanoparticles with Tunable Sizes

Splitting of water to hydrogen and oxygen on colloidal
catalysts
is a promising method for future energy and chemistry cycles. The
currently used high-performance oxides containing expensive elements
(Ru, Ir) are progressively being replaced by more sustainable ones,
such as Co<sub>3</sub>O<sub>4</sub>. Although the size of the nanoparticles
determines their catalytic performance, the control over the particles’
diameter is often synthetically difficult to achieve. An additional
obstacle is the presence of stabilizing agent, an organic molecule
that blocks accessible surface-active centers. Herein, we present
how precise control over size of the cobalt oxide nanoparticles (Co<sub>3</sub>O<sub>4</sub> NPs), their colloidal stability, and the ligand-free
surface affect overall performance of the photocatalytic oxygen evolution.
We accordingly correlated the photochemical results with the electrochemical
studies, concluding that accessibility of the active species on the
particles’ surface is crucial parameter in water oxidation.